Phase diagrams of polymer-dispersed liquid crystal systems of itraconazole – component immiscibility induced by molecular anisotropy Agnieszka Kozyra1, Naila A. Mugheirbi1,2, Krzysztof J. Paluch3, Grzegorz Garbacz4, Lidia Tajber1* 1School of Pharmacy and Pharmaceutical Sciences, Trinity College Dublin, Dublin 2, Ireland. 2Drug Product Science and Technology, Bristol-Myers Squibb, East Brunswick, New Jersey, 08901, USA. 3School of Pharmacy and Medical Sciences, Faculty of Life Sciences, Centre for Pharmaceutical Engineering Science, University of Bradford, Richmond Road, Bradford, W. Yorks., BD7 1DP, UK. 4Physiolution GmbH, Walther-Rathenau Strasse 49a, 17489 Greifswald, Germany. *To whom correspondence should be addressed:
[email protected] Phone: 00353 1 896 2787 Keywords: itraconazole, nematic, smectic, phase diagram, miscibility, Flory-Huggins theory, Maier-Saupe-McMillan theory 1 Abstract Liquid crystalline (LC) materials and their non-medical applications have been known for decades, especially in the production of displays, however the pharmaceutical implications of the LC state are inadequately appreciated and experimental data misunderstood leading to possible errors, especially in relation to physical stability of medicines. The aim of this work was to study LC phases of itraconazole (ITZ), an azole antifungal active molecule, and, for the first time, to generate full thermodynamic phase diagrams for ITZ/polymer systems taking into account isotropic and anisotropic phases that this drug can form. It was found that supercooled ITZ does not form an amorphous, but a vitrified smectic (vSm) phase with a glass transition temperature of 59.35 °C (determined using a 10°C/min heating rate), as evident from X-ray diffraction and thermomicroscopic (PLM) experiments. Two endothermic LC events with the onset temperature values for a smectic to nematic transition of 73.2±0.4 °C and a nematic to isotropic transformation at 90.4±0.35 °C and enthalpies of transition of 416±34 J/mol and 842±10 J/mol, respectively, were recorded.